Powell's first outpost in Seattle will only be open 11 days and will only be purchasing books, not selling them.

"This is our traveling show," said Miriam Sontz, chief executive officer of Powells.com. "We wanted to start it in Seattle for both geographical and emotional reasons. Then we may take it on the road to cities and towns with a high preponderance of college grads, places like Madison, Wis., and Charlottesville, Va."

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Powell's buying expedition to Seattle will settle into a rented space at 4321 University Way N.E., across from the University Book Store. It will operate daily from 11 a.m. to 7 p.m., from Sept. 9-19.

All kinds of books will be purchased by the Powell's buyers, except mass-market paperbacks (keep those romances with heaving cleavage at home). Particularly sought are books in the fields of science and technology. Textbooks also will be bought.

Powell's book purchasing is being held before the opening of the fall quarter at the University of Washington, in hopes that parking in the vicinity will remain readily available.

The uncertainty of how successful the new concept will be is causing some nervous stomachs in the Rose City book colossus.

"We have two scenarios," Sontz said -- "that we'll be overwhelmed with business, or that no one will show up."

Powell's, which long has sold new and used books, now buys between 3,000 and 5,000 used books every day in Portland.

"We'd love to buy that same amount in Seattle," Sontz said, "and if we bought 10,000 a day, we'd be thrilled."

Local used-book buyers and sellers said Powell's plan for Seattle is interesting but not likely to change the used-book market much. Lisa Perry, owner of Fremont's Twice Sold Tales, said she'd be worried if Powell's moved in next door and came to stay. But this unusual temporary foray doesn't amount to a threat.

"I've never heard of a store doing this," Perry said about Powell's brief lease. "I suspect they might end up getting other stores' rejects."

Perry said most people who sell books deal with the same store repeatedly. "I've never had any concern about getting books in the doors," she said. "It's a pretty steady stream." Powell's could advertise heavily and promise to pay more than anyone else, she said, but she's unsure how its buyers would do that and still sell books at a profit.

Hanna McElroy, co-owner of Magus Books in the University District, said she sees the Powell's effort as more positive than negative, even though the Portland store's buyers will set up temporary shop only a block away.

"It's going to drive some traffic to the neighborhood, so that's good," she said. "Ten days in and out is fine with me."

McElroy and her husband, Chris Weimer, have owned Magus since February. The store doesn't buy the textbooks Powell's wants. And she said she believes bookstores work better in clusters anyway. "Even if they set up shop (permanently), it would add a lot of vibrancy to the used-book-store market in the U District."

There long have been rumors that Powell's might one day enter the Seattle market as yet another independent bookseller. But Sontz added that a Seattle store is unlikely in the near future, since expansion here is not included in the company's current three-year plan.

"We are constantly in the process of re-evaluating those issues," Sontz said, "but we never say 'never.' "